linux-kernel - Re: [RFT][PATCH v1 0/5] cpuidle: menu: Avoid discarding useful information when processing recent idle intervals

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Message-ID: <29daaf17-7711-44b1-baad-86dadcf01666@arm.com>
Date: Fri, 7 Feb 2025 15:24:09 +0000
From: Christian Loehle <christian.loehle@....com>
To: Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
 "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Aboorva Devarajan <aboorvad@...ux.ibm.com>
Subject: Re: [RFT][PATCH v1 0/5] cpuidle: menu: Avoid discarding useful
 information when processing recent idle intervals

On 2/7/25 14:48, Artem Bityutskiy wrote:
> Hi,
> 
> thanks for the patches!
> 
> On Thu, 2025-02-06 at 15:21 +0100, Rafael J. Wysocki wrote:
>> Hi Everyone,
>>
>> This work had been triggered by a report that commit 0611a640e60a ("eventpoll:
>> prefer kfree_rcu() in __ep_remove()") had caused the critical-jOPS metric of
>> the SPECjbb 2015 benchmark [1] to drop by around 50% even though it generally
>> reduced kernel overhead.  Indeed, it was found during further investigation
>> that the total interrupt rate while running the SPECjbb workload had fallen as
>> a result of that commit by 55% and the local timer interrupt rate had fallen
>> by
>> almost 80%.
> 
> I ran SPECjbb2015 with and it doubles critical-jOPS and basically makes it
> "normal" again. Thanks!
> 
> Reported-by: Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
> Tested-by: Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
> 

I'll go take a look in-depth, honestly the statistical test of
get_typical_interval() is somewhat black magic to me before and after
4/5, so if that actually works better fine with me.
I'll run some tests, too.